In general, a plurality of semiconductor device chips formed on a wafer (semiconductor substrate) are tested for electric properties of each device and the like in a state of a wafer before cut into individual chips and sealed into packages, a so-called semi-finished product state. This testing of the wafer in the semi-finished product state is performed using a wafer tester called a wafer prober provided with a probe card including probe needles (probes) which contact electrodes of the wafer to apply test signals.
FIG. 13 is a front view schematically showing a wafer tester including a conventional probe card. As shown in the figure, the conventional wafer tester includes a wafer base 104 on which a wafer 103 constituting a testing object is to be mounted, and a probe card 101 positioned above the wafer base 104.
The probe card 101 includes a board 102 constituted of a printed circuit board or the like which transmits a predetermined test signal to be applied to each chip on the wafer 103 and a plurality of probe needles 120 arranged/fixed on the board 102.
The wafer base 104 is driven/controlled in a three-dimensional direction (arrow directions shown in FIG. 13) in such a manner that predetermined electrodes of the mounted wafer 103 contact the predetermined probe needles 120 of the probe card 101.
In the conventional wafer tester constituted in this manner, when the wafer base 104 is driven/controlled, the probe needles 120 of the probe card 101 contact the predetermined chip electrodes on the wafer 103. Moreover, test signals are applied to the electrodes of the wafer 103 from the tester via the board 102 of the probe card 101, and each device chip on the wafer 103 is subjected to a predetermined electric property test.
Here, in the conventional wafer tester, as shown in FIG. 13, the probe needles 120 disposed in the probe card 101 are constituted of needles formed of metals such as tungsten and the like, and a so-called cantilevered probe needle structure has been adopted in which a large number of metal needles are bent/formed into L-shapes, arranged on the board 102 having a plane disc shape, and fixed by a resin 130.
As the cantilevered probe needle, the metal needle having a total length of about 30 to 50 mm is bent/formed in such a manner that a needle height (arrow h shown in FIG. 13) on a tip side is about 10 mm. Even when there is a fluctuation in the height of the needle contacting the electrode of the wafer 103, the fluctuation can be absorbed within a limit of elasticity of the needle, for example, several μms. Moreover, a plurality of (e.g., several hundreds of) cantilevered probe needles are all arranged on the substrate, and bonded by an adhesive or the like by a manual operation.
However, a problem has occurred that the conventional probe card including the cantilevered probe needles cannot cope with the testing of highly densified and miniaturized wafers in recent years. In recent years, miniaturization and densification of semiconductor devices have remarkably advanced, and even the electrode on each chip has a micro size and interval (e.g., the electrode has one side of about 60 μm to 100 μm, and a pitch is about 100 μm to 200 μm).
In the conventional probe card, the cantilevered probe needle itself has a diameter of about 250 μm, all the probe needles have been attached by the manual operation, and therefore it has been impossible to attach a large probe needles at micro intervals on the substrate. Therefore, in recent years, the highly densified and miniaturized wafers have not been tested with the cantilevered probe card.
Additionally, in the cantilevered probe needle, there has been a problem that high frequency characteristics are deteriorated because the total length of the needle is about 30 to 50 mm.
Therefore, to solve the problem of the conventional probe card, a so-called membrane type probe card has been proposed in which a plurality of electrode bumps are formed on a thin film including a predetermined pattern wiring formed thereon and having flexibility instead of the cantilevered probe needles. Such a membrane type probe card is disclosed by Japanese Patent Application Laid-Open No. 1-128381 (page 4, FIG. 12), Japanese Patent Application Laid-Open No. 5-215775 (pages 3 and 4, FIG. 2), Japanese Patent Application Laid-Open No. 7-007056 (pages 4 and 5, FIG. 1), and Japanese Patent Application Laid-Open No. 8-083824 (pages 5 and 6, FIG. 3).
According to the membrane type probe card, fine processing of the electrode bumps formed on the thin film is possible, and therefore it has been possible to cope with the testing of the miniaturized and highly densified wafers.
However, the membrane type probe card has required a large number of complicated constituting elements such as a membrane including the electrode bumps, a holding structure which holds the membrane, and pressurizing means for energizing the membrane toward a wafer side.
Therefore, the probe card and wafer tester have been complicated and enlarged, and manufacturing costs have also increased as compared with the conventional cantilevered type.
The present inventor has realized that when silicon is etched or nickel plating or the like is used, it is possible to form a fine needle having a length of about 1 mm to 2 mm, and fine probe needles can be formed at high density and high precision without requiring the above-described membrane structure. However, thereafter it has been realized that even when the fine probe needles can be formed with high precision, and when the fine probe needles are simply mounted on the substrate, the needle heights of the probe needles are not uniform by unevenness of the substrate.
In general, for example, in a printed circuit board, the unevenness in height or flatness gently continues usually in a range of about 0.1 mm to 0.3 mm on the surface of the substrate. Therefore, when the fine probe needles having lengths of about 1 mm to 2 mm are mounted on this substrate surface, fluctuations are generated in the needle heights by the unevenness of the substrate. Additionally, the fluctuations cannot be absorbed within the elasticity limit by the probe needles having micro needle tips unlike the conventional cantilevered needle.
Therefore, as a result of further intensive researches, the present inventor has created a probe card of the present invention in which the problem of the unevenness of the substrate is solved and micro probe needles can be highly densely mounted.
That is, the present invention has been proposed to solve the above-described problem of the related arts, and an object thereof is to provide a probe card and a method of manufacturing the probe card in which probe needles to contact electrodes of a wafer are formed to be fine using silicon, nickel and the like and in which a flattened flat portion is formed on a substrate including the probe needles mounted/fixed thereon and in which fluctuations in needle heights are eliminated and micro probe needles can be arranged at high density and with high precision without requiring any complicated structure or the like.